Fletcher, Seth. Bottled Lightning: Superbatteries, Electric Cars, and the New Lithium Economy. New York: Farrar, Straus and Giroux, 2011.
This book is 273 pages in length (paperback version published by Hill and Wang, a division of Farrar, Strauss, and Giroux).
Although I would have preferred a most recently published book on batteries, I could not find one that appears to give as much detail as this, although the focus is on the most commonly used battery type. I decided to settle on this book because, even though it is 4 years old, its focus, lithium batteries, still dominates the energy storage field from smartphones to Tesla electric cars.
The author is a non-chemist but I did look at the bibliography and scanned through the chapters and noted that he based his information on reputable books and peer-reviewed journal articles. After a quick review scan of the chapters, I did see some level of detail in the chemistry discussion and it gives me hope that this will be an informative book for me and my search for a more detailed understanding of battery technology.
Seth Fletcher is a science writer and senior editor at Scientific American. http://www.scientificamerican.com/pressroom/expert-directory/
CHAPTER 1: THE ELECTRICIANS
In this chapter, the author gives a brief but detailed history of the discovery of electricity and the battery. There was period in the history of the United States when it looked like the electric car would come out to be a dominant player in transportation. The long time it took to come up with a better battery and the ease with which the gasoline engine became a more viable option ended the prospect of electric cars coming into the market. While improving upon his battery designed for cars, adding a lithium compound to the electrolyte was one of Edison’s solution to his first failed attempt. While this is not how lithium is used in so-called lithium batteries, the author used this as a starting off point to discuss lithium, its discovery, subsequent various uses, and its evolution into one of the most powerful elements to lead to increased energy density in today’s batteries.
· First documented observation of electricity is by Thales the Greek philosopher who rubbed amber with cloth (elektron is the Greek word for amber) and observed feathers being attracted to it.
· It was not until the beginning of the 17thcentury that the term electricity (from elektron) was coined by William Gilbert who observed that many materials can be “electrified” by friction.
· In the 1740’s, the Leyden jar was invented: a series of metals inside a jar immersed in some kind of electrolyte that acted like a capacitor, something that stores charge.
· Galvani observed what he attributed to electricity in the twitching of a dissected frog’s legs upon contact with a scalpel. Volta countered this with his own observation of metals contacting each other producing electricity. The two began a long-distance debate on the basis of this electrical phenomenon.
· In 1800, Volta reported constructing a device consisting of zinc-copper metal sandwiches immersed in brine that produced electricity. The term battery came from connecting a “battery” of Leyden jars connected in series.
· When this proved to be successful, bigger batteries were created to carry out all kinds of tests resulting in scientific discoveries: splitting of water into hydrogen and oxygen, breakdown minerals into newly discovered elements of potassium, magnesium, etc, electromagnetism, e.g.
· By the beginning of the 20th century, lead-acid batteries were being used to “power the telegraph, manage the load in the electrical-lighting substations, and support electric streetcar networks”.
· In 1898, Thomas Edison began earnest research into a new type of battery that would replace the rechargeable lead-acid batteries commonly used. He believed that an alkaline type would be lighter and more long-lived. In 1904, Edison launched a nickel-iron battery using a potassium alkaline electrolyte that have better properties than the lead-acid batteries: 14 watt-hours per pound and 233 percent “better”. Soon after, however, leaking and reduced capacities drove Edison to recall his batteries. The prospect of electric cars followed suit as gasoline engines steadily improved and gasoline cars became more affordable. Edison and his co-workers continued to solve the leaking and capacity reduction problems and in 1909 came out with a much-improved second generation A cell battery. Just around this time, however, the invention of an automatic starter for gasoline engines essentially wiped out any potential for the electric cars. The batteries, instead of running cars, became support energy sources for gasoline engines. Edison’s new battery saw use in running lamps and signals, telegraphy, and submarines but not electric cars.
· The two improvements that saved Edison’s battery were: the addition of nickel flake to the electrode and lithium hydroxide to the electrolyte.
· On lithium: as a metal, half the density of water, soft, very reactive with air and water. The author uses the term “volatile”. I think he means reactive.
· Berzelius is credited for having discovered lithium in 1817. Lithium is from the Greek word lithos meaning “stone”.
· Lithium salts are now used commonly to treat mental illness, prescribed as mood-stabilizing drugs such as Eskalith, Lithobid, Lithonate, and Lithotabs. It affects neurotransmitters and cell signaling, and is known to increase the production of serotonin.
· Of the 120,000 metric tons of lithium compounds mined each year, most go to metal alloys, ceramics, and lubricating greases. In addition its pharmaceutical use, other minor uses of lithium are in compounds that absorb CO2 in spacecrafts and other vessels, as rocket propellant, and in certain types of thermonuclear reactors. And, of course, the subject of this book, in batteries.
· An idea device for storing electricity is the smallest and lightest possible that can provide the largest stream of electrons. In lead-acid batteries, each electron comes from a heavy atom, lead, with an atomic weight of 207. In lithium batteries, an electron can be squeezed out of a much smaller atom of lithium with an atomic weight of 7.
· In addition, lithium’s reactivity and willingness to give up an electron means produces batteries that are high in energy density.
· In 2010, Bill Gates noted that all the batteries in the world can store only 10 minutes of the global energy need.
· The author has the following to say about the advantages of using electricity to run vehicles: "Mile by mile, it’s cheap compared with gasoline. It’s far more feasible than hydrogen, and in almost all circumstances it’s cleaner than ethanol. It can come from almost any source – natural, gas, coal, nuclear, hydroelectric, solar, wind. Even when it is generated by a coal-burning plant, it still produces less carbon dioxide per mile than a mile of gasoline.”
CHAPTER 2: FALSE START
We have only two modes— complacency and panic. —James R. Schlesinger, first U.S. secretary of energy
Fletcher, Seth (2011-05-10). Bottled Lightning: Superbatteries, Electric Cars, and the New Lithium Economy (p. 22). Farrar, Straus and Giroux. Kindle Edition.
In this chapter, the author tells the story of the revival of strong interest in electric cars due to increased air pollution reaching a crisis level and an international oil emergency and mismanagement that caused oil shortages in the late 1960’s to early 1970’s. These intersections of events catalyzed research in electric car batteries and, after 1973, Exxon was able to demonstrate a prototype of the first rechargeable lithium battery in a Society of Automotive Engineers conference. After 1973, Exxon was able to demonstrate a prototype of the first rechargeable lithium battery in a Society of Automotive Engineers conference. After a few more attempts at trying other chemical material, in 1976, Whittingham published a paper in science on a LiTiS2battery. The momentum continued as the world continues to have unreliable and affordable sources of petroleum. In 1973, the Arab Oil embargo began. In a Forbes magazine article, there were speculations of Exxon’s possible demise as there were indications of oil running out: “Unless the presently unexpected occurs, the world’s petroleum reserves are within a few years of their peak and will begin a slow decline to the point where oil and gas will be too valuable to use as energy”. In 1976 (during Ford’s presidency), Congress passed the Electric and Hybrid Vehicle Research, Development, and Demonstration Act, aimed to stimulate research, development, and production of alternatives to gasoline engines. Exxon marketed the first widespread use of lithium batteries for solar digital watches. These lithium cells had a major advantage over nickel-cadmium batteries that bled energy away quickly and silver-zinc batteries that died after only 20-25 recharges. Exxon continued to invest in electrical devices, purchasing a company that made electric motors. GM got in the game as well building an electric car in 1979 while Exxon built a prototype hybrid car. But, the electric car industry never took off and interest in alternative fuels plummeted due to the following reasons: recession in 1979-1980 brought unprofitable ventures in to solar panels and batteries to a halt; by 1986, oil was again below $15 a barrel and supplies were steady as governments and oil companies ramped up their search for cheaply extracted oil reserves in the preceding years finding them in Alaska, the North Sea, and Mexico; and conservation measures mandated by the American Corporate Average Fuel Economy set average mpg at 27.5 saving 2 million barrels of oil a day between 1975 and 1985. Reagan introduced further cutbacks in renewable energy programs when he came into office. In the end, the best battery developed during that “false start era” could only store 30-35 watt-hours/kg, 500 times less energy density than gasoline. The following statement summed up how companies responded to this new era of oil abundance with respect to the development of batteries and other alternatives: “The key to the feasibility of advanced batteries of all types is the price and supply of oil”.
· Increasing air pollution that, in the extreme case, forced residents to wear nose masks indoors in LA, only 4 decades after the availability of the gasoline car drove the state of California to create laws to decrease the amount of air pollution created by cars. It mandated that any new car manufactured should be built with a system that redirects any unburned fuel back to the engine for combustion instead of to the tailpipe as part of the exhaust.
· Anti-gasoline car sentiments grew and politicians were driven to pass the Clean Air Act of 1970.
· Around this time, the oil geopolitical crisis in the Middle East also started and international dispute and mismanagement caused an oil shortage that caused 1/5 of the gasoline stations in the US to run out of gasoline.
· Although there were strong sentiments to revive electric cars, no battery technology existed at that time to replace the versatility and efficiency of the gasoline engine. The electric car technology was behind gasoline technology 60 years by this time.
· During that time, current research on the solid state ion movements had promising ideas for a new battery design. The current design of lead acid batteries had reactions taking place only on the electrode surface in contact with the electrolyte leaving the core metal unused. Therefore, much greater capacities can be attained if these reactions that produce electrons can take place in a three-dimensional volume. (Robert Huggins’s and group at Stanford.)
· In Ford in 1967, researchers have come out with a reversed battery design in which the electrodes are liquid (molten sodium and sulfur, heated at 300 C) separated by a solid ceramic electrolyte. The ceramic was a form of aluminum oxide called beta-alumina that allowed ions to diffuse but not electrons.
· By 1972, a conference was held on the very narrow topic of applications of solid state chemistry to battery design where participants wondered about and discussed exotic but theoretically possible pairings of elements for new batteries: sulfur-sodium, lithium-sulfur, magnesium-oxygen, zinc-air, aluminum-air, lithium-copper fluoride, etc. At the same time, American car companies Ford, GM, Chrysler, and American Motors, Toyota, and German car companies were all working on electric cars.
· In addition to the Belgirate conference group, Argonne National Lab, Bell Labs, Electric Power Institute, Dow Chemical, and General Electric were putting in their share of chemical research into batteries. Even Exxon got into it.
· Whittingham at Exxon came up with a battery design with a theoretical energy density of 480 watt-hours per kilogram, more than twice what was generally thought necessary to run an electric car. It uses titanium disulfide and lithium as the negative electrode (he first experimented with tantalum disulfide and realized this was too heavy to be viable car batteries). At this point, Japan had already introduced the use of lithium in non-rechargeable batteries for lamps used by fishermen.
· Exxon put in the money to build a prototype. The step was to determine what suitable electrolyte to use:
o Extremely low freezing point, -30 C
o Not an electrical conductor but allow ions to flow through but not electrons
o Able to dissolve salts that contain the right ions needed for the electrochemical reaction
· After 1973, Exxon was able to demonstrate a prototype of the first rechargeable lithium battery in a Society of Automotive Engineers conference. After a few more attempts at trying other chemical material, in 1976, Whittingham published a paper in science on a LiTiS2 battery.
· In 1976 (during Ford’s presidency), Congress passed the Electric and Hybrid Vehicle Research, Development, and Demonstration Act, aimed to stimulate research, development, and production of alternatives to gasoline engines.
· In 1973, the Arab Oil embargo began. In a Forbes magazine article, there were speculations of Exxon’s possible demise as there were indications of oil running out: “Unless the presently unexpected occurs, the world’s petroleum reserves are within a few years of their peak and will begin a slow decline to the point where oil and gas will be too valuable to use as energy”.
· The first ever rechargeable lithium battery to be sold in the market were button-size cells for watches. The first widespread use of lithium batteries were for solar digital watches in which they were recharged by solar cells. These lithium cells had a major advantage over nickel-cadmium batteries that bled energy away quickly and silver-zinc batteries that can died after only 20-25 recharges.
· Exxon continued to invest in electrical devices, purchasing a company that made electric motors because as Exxon’s chairman said in July 1979, “We’re not finding as much oil as the world is using…in the long term, I’d say that you don’t ignore any source of energy. We can’t go back to the complacency of two years ago”. The author notes that “Exxon had no desire to build electric cars itself, (Garvin) said, but through Reliance, he hoped to supply the motors, and through the Battery Division, the power”.
· GM got in the game as well building an electric car in 1979 while Exxon built a prototype hybrid car.
· But, the electric car industry never took off and interest in alternative fuels plummeted:
o Recession in 1979-1980 brought unprofitable ventures in to solar panels and batteries to a halt
o By 1986, oil was again below $15 a barrel and supplies were steady as governments and oil companies ramped up their search for cheaply extracted oil reserves in the preceding years finding them in Alaska, the North Sea, and Mexico.
o Conservation measures mandated by the American Corporate Average Fuel Economy set average mpg at 27.5 saving 2 million barrels of oil a day between 1975 and 1985
o “Reagan came in and cut back energy efficiency and renewable energy program by something like eighty percent”.
· In the end, the best battery could only store 30-35 watt-hours/kg, 500 times less energy density than gasoline. The following statement summed up how companies responded to this new era of oil abundance with respect to the development of batteries and other alternatives: “The key to the feasibility of advanced batteries of all types is the price and supply of oil”.
CHAPTER 3: THE WIRELESS REVOLUTION
In this chapter, the author traces the development of wireless devices, ones that would later on become the major consumer of rechargeable lithium ion batteries. Parallel to this is an account of the work done by the scientist Goodenough in developing the technology for the three major strains of lithium batteries in use today. Aside from the invention and the eventual market debut of the wireless phone, a mini-electronic gadget explosion in Japan also provided the market motivation to develop better batteries with less toxic materials. Pollution and accidental ingestion of batteries had reached a crisis point in Japan at that point due to their massive use of ever-smaller batteries. Despite an initial partnership with Union Carbide to develop lithium battery technology, Sony eventually became the main owner and developer after the Bhopal accident led to the demise of Union Carbide. In the late 1980’s, Sony came out with the newly developed lithium-ion battery that carried a 3.6 voltage (3 times that of NiCad and NiMH) and therefore a higher energy capacity, extraordinary recharging capability, and not subject to the memory effect that causes batteries recharged before they are dead to lose energy capacity. Interspersed in the Sony success is the story of the failed lithium batteries developed and manufactured by Moli using a molybdenum lithium disulfide material. This battery required metallic lithium. Several fire accidents caused the company to lose its business which was sold to a Japanese company. Meanwhile, the cell phone industry flourished and was soon in need of a battery “with longer life and less weight”. Battery size needed to keep up with the rapid miniaturization taking place with electronic gadgets as smaller processors are invented. In 1992, Sony came out with a lithium ion battery that was 30 percent smaller and 35 percent letter than then leading NiCad battery. Its storage capacity was 90 watt hours per kilogram; triple that of lead-acid, nearly double that of NiCad, and 10-20 percent better than NiMH. At the same time, cell phone use continued to proliferate as it becomes smaller and lighter in size. In 1993, 13 million cell phones have been sold in the US and the price was 25 percent cheaper than the year before. In 1994, Motorola released the first cell phone run by a lithium ion battery, weighing a mere 3.9 pounds, lighter than a D-cell. Sadly, Goodenough never got any monetary rewards for the work he did on lithium battery technology. Further miniaturization occurred with the invention of the 3-volt RF amplifier allowed even smaller cell phones that now only require 1 lithium ion battery. By 1998, there were more than 240 million cell phone subscribers. By 1999, the cell phone began its evolution into a smart phone. By 2002, 95% of cell phones were using lithium ion batteries, which the Economist called the “foot-soldiers of the digital revolution”.
· In 1947, two Bell Labs scientists (Ringer and Young) were working on the development of a cell phone, one that is based wirelessly on a series of radio transmitters distributed over a large geographical are to provide cells of radio coverage. By 1973, Motorola had developed the first mobile phone.
· Goodenough would develop the three major strains of lithium cells used today. Goodenough’s work on the lithium battery started with replacing the sulfide in Whittingham’s design with an oxide because he knew he can get more voltage out of it. Tests on several variations of LiMO2 (where M= transition element) resulted in a lithium cobalt oxide cathode which allowed removal of as much as half the lithium and still have a stable substance with a voltage of 4 volts, higher than Whittingham’s 2.4 volts. In addition, instead of building the battery fully charged, the battery was constructed in the discharged state allowing use of compounds that are stable at ambient conditions (obviating special lab conditions such as a dry room or an argon chamber). In 1980, Goodenough published his results on the lithium cobalt oxide type.
· Despite this, there was no movement partly due to the federal government taking about a decade to decide on regulations of frequencies companies can use to carry calls.
· Outside the US, however, in the early 80’s, cell phone towers were going up in Japan, Bahrain, Saudi Arabia, Mexico, and the Scandinavian countries.
· In October 1983, the first US cellular network was launched, using the Bell Labs vision of distributed low-power cell towers to carry the signals with a phone assigned a new frequency as it moved to the next “cell” region. In 1984, the first handheld mobile phone went on sale.
· During this time, a mini-electronic gadget craze in Japan has fueled a battery pollution crisis and ingestion health hazard due to ever-smaller batteries being used. This provided an impetus to develop better batteries that have less toxic materials. In the US, however, there was no strong response and new battery development remained largely unmotivated and Goodenough’s new lithium batteries did not find any takers. The focus was on semi-conductor instead, ceding the R & D on lithium battery technology to Japanese companies.
· Although a partnership eventually developed between Japans Sony Corp and Union Carbide, the Bhopal Disaster (release of methyl isocyanate that killed thousands) led to the dismantling of Union Carbide. Sony bought all of the lithium battery technology and decades of publications by Whittingham, Goodenough and others. In the late 1980’s, the Sony team came up with a safe and cheap lithium battery for commercial production and sale. It uses a carbon anode and a cobalt oxide cathode and the following reaction:
o LiC6 + CoO2 àC6 + LiCoO2.
o P = IV, V = 3.6 volts; the higher voltage allows greater power at the same current
o This represented a major jump in voltage and doubling of energy capacity.
o As a comparison, it took 6 of a nickel-cadmium 1.2 V batteries connected in series to provide the 7 volts needed to run a mobile phone. It would only take two of the new lithium batteries.
o Sony’s lithium battery lasts longer too because it is “extraordinarily” rechargeable.
o Did not suffer from “memory effect” like the NiCad and NiMH that causes loss of energy capacity if recharged before completely dead.
o Sony named these batteries lithium ion batteries.
· Interspersed in the Sony success is the story of the failed lithium batteries developed and manufactured by Moli using a molybdenum lithium disulfide material. This battery required metallic lithium. Several fire accidents caused the company to lose its business which was sold to a Japanese company.
· Meanwhile, the cell phone industry flourished and was soon in need of a battery “with longer life and less weight”. Battery size needed to keep up with the rapid miniaturization taking place with electronic gadgets as smaller processors are invented.
· In 1992, Sony came out with a lithium ion battery that was 30 percent smaller and 35 percent letter than then leading NiCad battery. Its storage capacity was 90 watt hours per kilogram; triple that of lead-acid, nearly double that of NiCad, and 10-20 percent better than NiMH.
· In 1993, 13 million cell phones have been sold in the US and the price was 25 percent cheaper than the year before. In 1994, Motorola released the first cell phone run by a lithium ion battery, weighing a mere 3.9 pounds, lighter than a D-cell.
· In a side note, Goodenough never got any monetary rewards for the work he did on lithium battery technology.
· By the late 1990’s, the invention of the 3-volt RF amplifier allowed even smaller cell phones that now only require 1 lithium ion battery.
· By 1998, there were more than 240 million cell phone subscribers. By 1999, the cell phone began its evolution into a smart phone.
· By 2002, 95% of cell phones were using lithium ion batteries, which the Economist called the “foot-soldiers of the digital revolution”.
CHAPTER 4: REVIVING THE ELECTRIC CAR
In this chapter, the author starts off by telling a brief story of the Tesla Company that now builds electric cars “that compete on performance rather than price”. One of the founders, Eberhard, used money from the sale of his company to put together a group of people that would build the “hottest” electric car around. In 2003, Tesla Motors was incorporated. Eberhard had lithium ion batteries in mind even at the start. Their battery pack design consisted of 6,831 laptop batteries. One of the things they had to deal with was a thermal runaway problem associated with lithium ion cells. In one test, they watched a pack of lithium ion cells catch fire and turn into an inferno after deliberately overheating it. In July 2006, Eberhard et al went public and showed the Tesla Roadster. Meanwhile, over at GM, Bob Lutz was steaming with frustration as he watched the launch of the Tesla and the popularity of the Prius rise while his ideas of a GM electric car were held back by lack of enthusiastic support from the company. To Lutz” Nothing less than an electrically driven car would appease these critics. Lutz’s argument was, “Whether we like it or not, there are the environmentally conscious people, the government people in California, the car people— everybody seems to believe that the electric vehicle is the answer. And with the advent of lithium-ion batteries, I think that we’re getting to the point where it is feasible.”” In 2007, GM finally came out with the Chevy Volt with much positive press. “Lutz described the drivetrain and the specifications. Forty miles on lithium-ion batteries alone. If you’re one of the 78 percent of Americans who live within twenty miles of work, and you charge the car every night, “You will never need to buy gasoline during the entire life of the vehicle,” he said, and that line drew enthusiastic applause. “And you would save five hundred gallons of gasoline and eliminate 4.4 metric tons of carbon dioxide a year from the tailpipe.” If you drive sixty miles a day, you’ll get the equivalent of 150 mpg, he said. Use E85 and you’ll get more than five hundred miles per equivalent petroleum gallon.”
CHAPTER 5: THE BLANK SPOT AT THE HEAR OF THE CAR
In this chapter, the author gives an account of the historical struggles of the electric cars due to various social, cultural, economical, and infrastructure issues, starting back in the late 19th century. In the number of false starts described by the author, however, a common denominator was the limitations imposed by the battery system, referred to by the author as "the blank spot at the heart of the car". When the concept of an electric car was first introduced, electricity was still a mysterious phenomenon for most people. But, in the late 19th century and early 20th century, what eventually killed any prospects for the electric car is the development of gas powered engines. Electric cars were plagued with limited range, charging, and battery maintenance issues that made it easy for the gasoline engine to take it over as the engine of choice.
In the 1950's and 1960's, increasing pollution problems from gasoline combustion stimulated some interest again in developing electric cars. A few electric car prototypes came out of Detroit in 1966 but even the oil crisis of the 1970's did not result in the further development of electric cars. In the 1990's, the California Air Resources Board issued a mandate for 2% of all cars sold in CA starting 1998 must be emission-free. This created a short but doomed "boomlet" of electric car production by GM and its competitors. A quote from the New York Times given by the author provides a cynical interpretation that GM was producing an electric car simply to prove the government wrong about its viability and marketability. The EV1 was produced and there was higher than expectation demand for a lease but eventually the state capitulated by postponing the deadline. In the author's words, "But while GM was rolling in positive press as a result of the EV1, it was simultaneously lobbying the state of California to dismantle the CARB regulations. The company argued that this legislation was forcing a private enterprise to produce, at enormous."..."General Motors and DaimlerChrysler eventually succeeded in beating CARB down. GM built the last EV1s in 1999; that generation used nickel- metal- hydride batteries and could run up to 150 miles on a charge." Eventually, GM recalled all the EV1's ever leased, hauled them out to the desert where they were all crushed to death.
GM's next and latest attempt at an electric vehicle came several years later in its announcement of the new Chevy Volt electric car, a car cynically referred to by a New York Times op ed as truly a car of the future considering when the concept was released, there was not battery technology available to run it. Even the Wall Street Journal was scathing in its criticism that GM simply wanted to appear fuzzier to further encourage government bailout. Nevertheless, there were serious efforts to launch the Volt which started with a hunt and competition for the best batteries. The final contenders in this search were CP1 and A123. The specifications required by GM included: "Each supplier had to prove that its product could store 16 kilowatt- hours of energy, drive the Volt forty miles on electricity alone, launch the car from zero to sixty in eight seconds, run for at least ten years, withstand five thousand full discharges, lose no more than 10 percent of its charge capacity along the way, fit into the tunnel that houses a conventional car’s driveshaft, weigh no more than four hundred pounds, and cost as little as possible. And never, ever explode." The final battery pack for the first test cars consisted of 200 3.6 volt lithium ion cells packed in groups of three surrounded by a cooling liquid. " A computerized monitoring system inside each battery pack conducted this little orchestra, coordinating the actions of the individual cells, balancing voltage, and watching, above all, for any indication that a cell might be failing, shorting out, or otherwise threatening the stability of the system. The batteries were engineered to propel the 3,520- pound Volt forty miles." This time, the atmosphere that the Volt was announced in portend a more motivated market for the electric car: gas was $4 a gallon, there was desperation among the American carmakers brought on by the recession, global warming was becoming a more serious public issue, and lastly, the blank at the center of the heart of the electric car has now been filled by a more improved lithium ion battery technology.
